Stored program controlled telephone switching systems are used to interconnect telephone station sets as well as digital terminals, personal computers and large mainframe computers. The telephone switching system establishes data communication connections between computer facilities in a manner analogous to voice communication connections between subscribers using analog telephone station sets. Each of the computer facilities are connected to an associated communication pair of the telephone switching system by a modem. A standard telephone station set is also connected to the communication pair and is used to originate a call to a destination computer facility. As a result of the call origination, a communication connection is established through the telephone switching network from the originating telephone station set to the destination computer facility. The user then switches the modem on line and the modem converts the digital signals output by the computer facility to analog signals which are transmitted by the switching network to a modem associated with the destination computer facility. The destination modem converts the received analog signals to digital signals for use by the destination computer facility.
Thus, the telephone station set is used for call origination purposes so that the computer at the originating location can be connected to the telephone lines.
An alternative arrangement is where the computer facility is directly connected to the communication pair through an interface circuit and the computer facility emulates the functions of the telephone station set. In this case, the originating computer usually displays the telephone station set buttons and key pad on the screen of the video display terminal (VDT) associated with the computer facility. The user can use the cursor on the VDT to select various telephone station set buttons displayed on the VDT so that the associated telephone function can be activated. The computer responds to the cursor movement by emulating the telephone station set function identified by the user. In this fashion, the digital telephone station set is no longer needed for call origination purposes. The computer facility can perform all the functions previously associated with the adjunct telephone station set.
Neither of these prior art arrangements provide communication services on the computer system for the associated telephone station set. The telephone and computer functions are independent and mutually exclusive.